Aftermarket Sparkplugs

[jkuchta]

Has anyone here changed out the stock plugs for aftermarket plugs? Marketing hype being what it is, I'm not sure $10/per is worth any MPG or HP gain. I know the stock plugs are good, and I only have a little more than 18k miles on the car, but a few mpgs would be worth the expense if there was a desent return.

As a note, I'm looking more for MPG than HP...lets not kid ourselves here, I drive the car to work, and bought it based on price, durability, and economy.

Note, since new I've averaged 37-38 mpg, 50/50 hwy./city driving in Southern California, using Shell V-Power and Castrol full synthetic, changed at about 3k intervals. Also, I've installed a K&N filter in the stock housing.

Thanks in advance.

[xpeteyjtx]

I don't think you will see a noticeable gain. You already have Densos or maybe NGKs from the factory which are a perfect match for your car from a design standpoint. You will see more MPG by adjusting your driving habits.

[PetersRedYaris]

The stock spark plugs are iridium and basically as good as you can get. They are rated for 100,000 miles so don't even worry about them.

[caveatipse]

The stock Yaris plugs are actually very good.

[Ferret_san]

I've never noticed any difference in my cars by changing the sparkies, but in the past, I've noticed a significant improvement in responsiveness when changing the leads.